—Would you like to go to the cinema with me tomorrow afternoon?—I’d like to, Mum, but I ________ to a party by Jane. It is her birthday.
--How often do you drop your English teacher a line? ---________. But usually once a week.
Some English scientists are identifying problems ____ technology in the 21st century. If solved, the solutions could change the world.
Exactly ____they did when at last they reached the sea remains a complete mystery.
One thing’s for sure, the fire _____by some cigarette butts.
You could ________ this a really nice room if you bought a new carpet.